https://www.codewars.com/kata/5ab6538b379d20ad880000ab/
You are given the length and width of a 4-sided polygon. The polygon can either be a rectangle or a square. If it is a square, return its area. If it is a rectangle, return its perimeter.
area_or_perimeter(6, 10) --> 32
area_or_perimeter(3, 3) --> 9
Note: for the purposes of this kata you will assume that it is a square if its length and width are equal, otherwise it is a rectangle.